Is there a way to prevent pipe overflow in Buildcraft?

You can use obsidian pipes to redirect the outputs of chests. Take the following test rig:

I have filled the chest with buckets, as a sample:

If you pipe another item into the chest, it will simply pop out of the pipe, like so:

Fortunately, obsidian pipes do not connect to themselves, so you can use this to create a somewhat compact device to channel additional items elsewhere. Here's a possible system:

The iron pipes will keep the items from flowing directly into the new chests, and the obsidian pipes will pull in items that overflow.

You can also use more powerful engines of course, if you want to. This is all just an example.

A green insertion pipe will do the trick, and, you can easily chain them to fill 20 chests or machines.